July 24 (Reuters) - British lender Metro Bank said on Tuesday it would raise about 300 million pounds ($394 million) through a share placing and reported higher first-half underlying pretax profit, setting it on track for its second full year of profitability.

Metro Bank, founded in 2010 to help break the dominance of Britain’s biggest banks, said underlying profit before tax rose to 24.1 million pounds in the six months ended June 30, up sharply from 6 million pounds a year ago, driven by strong growth in residential mortgages and commercial lending.

The lender said it planned to raise capital through a non-pre-emptive cash placing of up to about 8.85 million new shares at a price of 3,422 pence per placing share.

Metro Bank said the proceeds of the placing would be used for growth and to replace funds used for its acquisition of a mortgage portfolio for 597 million pounds.

CEO Craig Donaldson had said in February that the lender may raise capital this year as the British challenger bank looked to more than double its loan book within three years.

Metro Bank raised 278 million pounds last year by selling new shares to investors.

The company said in April that it expected to issue up to 250 million pounds of new debt this year, stoking concerns it may need to raise even more capital to challenge the country’s biggest banks.

Analysts have said that institutional shareholders could tire of cash calls.

Metro Bank, the first new high street bank in Britain in over 100 years when it launched in 2010, said total revenue rose 45 percent to 189.8 million pounds during the period.

The company said customer accounts rose by 201,000 to 1.4 million at the end of the period from Dec. 31, 2017.

A company spokesman said the placing announcement had triggered a disclosure of interim results, that had initially been scheduled for release on Wednesday. ($1 = 0.7613 pounds) (Reporting by Noor Zainab Hussain and Justin George Varghese in Bengaluru; editing by David Evans and Adrian Croft)